Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$159.84	9.425%	$174.9049	$174.90	$174.90	$174.90
Purchase #2	$142.60	12.813%	$160.8713	$160.87	$160.85	$160.90
Purchase #3	$185.56	5.723%	$196.1796	$196.18	$196.20	$196.20
Purchase #4	$58.81	6.346%	$62.5421	$62.54	$62.55	$62.50
Purchase #5	$167.74	3.750%	$174.0303	$174.03	$174.05	$174.00
Purchase #6	$167.52	7.533%	$180.1393	$180.14	$180.15	$180.10
Purchase #7	$21.75	13.590%	$24.7058	$24.71	$24.70	$24.70
7 purchase totals =	$903.82		$973.3733	$973.37	$973.40	$973.30